Method and apparatus to reduce noxious components in the exhaust emissions of internal combustion engines

ABSTRACT

To provide for rapid and effective control upon persistent deviation of control signals, derived upon integration of sensed output signals representative of exhaust emission, beyond a predetermined time, the base setting of a fuel injection system, or a carburetor system, is changed in a direction to counteract the deviation, for example by extending (or reducing) fuel injection time beyond the range of change within the fuel injection circuit, for example by additionally modifying the charge level of a storage capacitor; or, in a carburetor system, by controlling bypass of air, or the setting of a fixed jet.

nited States Schmidt et al.

atent [191 Mar. 18, 1975 METHOD AND APPARATUS TO REDUCE NOXIOUS COMPONENTS IN THE EXHAUST EMISSIONS OF INTERNAL COMBUSTION ENGINES Robert Bosch GmbH, Stuttgart, Germany Filed: Aug. 20, 1973 Appl. No.: 390,013

Assignee:

Foreign Application Priority Data Sept. 28, 1972 Germany 2247656 References Cited UNITED STATES PATENTS 6/1973 Loos 123/32 EA M n, 1-, v,

3,745,768 7/1973 Zechwall 123/32 EA 3,759,232 9/1973 Wahl 123/32 EA 3,782,347 1/1974 Schmidt 60/276 Primary Examiner-Charles .1. Myhre Assistant Examiner-R0nald B. Cox Attorney, Agent, or Firm-Flynn & Frishauf To provide for rapid and effective control upon persistent deviation of control signals, derived upon integration of sensed output signals representative of exhaust emission, beyond a predetermined time, the base setting of a fuel injection system, or a carburetor system, is changed in a direction to counteract the deviation, for example by extending (or reducing) fuel injection time beyond the range of change within the fuel injection circuit, for example by additionally modifying the charge level of a storage capacitor; or, in a carburetor system, by controlling bypass of air, or the setting of a fixed jet.

ABSTRACT 10 Claims, 7 Drawing Figures FUEL INJECTION CONTROL CKT EXHAUST SENSOR ONTROL AMPLIFIER I ,XIENIEU II'III I 8 I375 SIILEI 1 [If 4 EXHAUST SENSOR AMPLIFIER ONTROL FUEL INJECTION CONTROL CKT {"QIJEPJTEBILKRI85975 3871 I338 WI 2 UP 4 68 FUEL INJECTION VALVE S5 SOLENOID 69 O 57 SWITCHING AMPLIFIER METHOD AND APPARATUS TO REDUCE NOXIOUS COMPONENTS IN THE EXHAUST EMISSIONS OF INTERNAL COMBUSTION ENGINES CROSS REFERENCE TO RELATED PATENT AND APPLICATIONS U.S. Pat. No. 3,483,851, Reichardt, Dec. 16, 1969.

The present invention relates to method and apparatus to reduce the noxious components in the exhaust emmission of internal combustion engines, and more particularly of automotive internal combustion engines, in which a controller is provided which has integrating characteristics, to control the proportion of air and fuel being supplied to the internal combustion engine.

It has previously been proposed to reduce the noxious components in the exhaust emmission of internal combustion engines by sensing the composition of the exhaust gas by means of a sensor, located to be exposed to the exhaust gases, and then to control the proportion of air and fuel in such a manner that the proportion is just below the stoichiometric value. This proportion of fuel to air is also referred to as the air number A. When A l.0, the mixture of air and fuel is exactly at the stoichiometric value (approximately 14.4:1). Controlling the air number A to a slightly lower value, for example A 0.98 results in emission of exhaust gases in which the carbon monoxide and hydrocarbon components have a low value. It is necessary, however, that the value of h be controlled to have only very small tolerance, so that the exhaust emission does not exceed permissible limits. Controlling the tolerance of h, in the previously proposed apparatus, and in accordance with previously proposed methods is done by controlling the voltages at the output of a control amplifier by means of a proportionality element, such as a potentiometer, or the like. So controlling the tolerance results in a limitation of the entire range of control by the supply or -iions of the internal combustion engines, it is necessary to expand the range of control. For example, if the internal combustion engine is started while hot, or to protect a catalytic reactor in the'exhaust system if ignition partly fails in the engine, it is necessary to have a wider range of limits between which the controller may operate.

It is an object of the present invention to provide apparatus and a method to reduce noxious components in the exhaust emission of internal combustion engines, and in which the control limits, or the control range of the controller is expanded in a simple, and effective manner, to better control the air number A. The apparatus to carry out the method should, further, be sturdy and suitable for the rough and widely varying conditions which arise in automotive applications, and the apparatus should utilize as much as possible of already available and existing devices and apparatus in usual automotive engines, or automotive vehicles.

SUBJECT MATTER OF THE PRESEN INVENTION Briefly, the control range of the control apparatus is changed in dependence on at least one-operating parameter of the internal combustionengine, and the base setting of the air-fuel supply device is accordingly changed in one direction, or the other. The air-fuel supply device may, for example, be a fuel injection system and changing the operating range thereof includes changing fuel injection time; or, for instance, it may be a carburetor, and changing the air-fuel mixture may involve adding additional air, or additional fuel through a separate jet, or by changing the setting of a jet, or opening or closing an air bypass, more or less.

In accordance with a feature of the invention, a threshold switch is provided which responds when a certain operating parameter is exceeded, the threshold switch upon response, changing the base setting of the air-fuel supply device to the internal combustion engine.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a highly schematic diagram illustrating the system with which the invention is used;

FIG. 2 is a diagram illustrating the relationship of output voltage with respect to air number A of an exhaust gas sensor;

FIG. 3 is a schematic abbreviated circuit diagram of a control amplifier;

FIG. 4 is a fragmentary, abbreviated circuit diagram of a transistor fuel injection circuit;

FIG. 5 is a circuit diagram of apparatus to change the control range of a fuel injection control device;

FIG. 6 is a series ofgraphs illustrating the operation of the circuit of FIGs. 3, 4, and 5; and

FIG. 7 is a highly schematic representation of the fuel and air supply to an internal combustion engine, utilizing a carburetion system, and adjustment of the system in accordance with the invention.

For purposes of illustration, the invention will be described in connection with a four-cylinder engine 11 (FIG. 1) to which air is supplied over an inlet air filter 12 through an induction duct 13. Throttle 15 is located in duct 13, the throttle position being controllable by the accelerator pedal. An air mass flow meter 14 is located in duct 13 between filter l2 and throttle 15, which has an electrical output line B. The mass air flow meter may be a spring-biased disk. One, or more fuel injection valves 16 are associated with the internal combustion engine 1 1; preferably, a fuel injection valve 16 is provided for each of the cylinders, immediately adjacent the inlet valves thereof, and injecting fuel into the inlet manifold adjacent the inlet valves. Only one of the injection valves 16 is shown for simplicity. A fuel supply line 17 provides fuel to the injection valves.

An exhaust manifold 18 is connected to the exhaust side of the engine, which terminates in a thermo reactor 19, the output of which is connected to a catalytic reactor 20. The exhaust system itself is connected to the output of catalytic reactor 20, forming an exhaust pipe 21 which is connected to the usual muffler, and the remaining portions of the exhaust system, which can be standard (not shown). The thermo reactor 19 and the catalytic reactor 20 provide for after-treatment of the exhaust gases.

An exhaust gas sensor 22 is connected in the wall of the connection pipe from the thermo reactor 19 to the catalytic reactor 20. A tachometer generator 23 is connected to the crankshaft of the engine 11 to provide control pulses in synchronism with rotation of the engine for a transistorized fuel injection controller 25.

The transistorized circuit 25 provides pulses which have pulse durations determining the opening time of the injection valve 16. The pulse duration is influenced by the electrical data derived from the air mass flow meter 14 and the control amplifier 24. The outputs of control amplifier 24 and of the mass air flow meter 14 are connected to the inputs A, B of a transistor circuit 25, which form command input terminals. Injection valve 16 is operated by means of a solenoid, connected in the output of the circuit 25.

The diagram of FIG. 2 shows the output voltage from sensor 22 with respect to air number A. As can be clearly seen, the value of the output signal changes abruptly between two terminal, or saturation values at about a value of )t 1.0. When the mixture is lean, )t l.0; a rich mixture has a )t l.0.

The output signal from sensor 22 is applied to the control amplifier 24, shown in detail in FIG. 3, to control the relative quantity of air and fuel being supplied to the engine. Control amplifier 24 (FIG. 3) includes a first operational amplifier 40 which provides proportional amplification of the output signal of sensor 22, and a second operational amplifier 47, connected as an integral controller. The oxygen sensor 22 is connected over input resistor 41 to the inverting input of operational amplifier 40, and, with its other terminal, to ground or chassis. The non-inverting input of operational amplifier 40 is connected over input resistor 42 to the tap point of a voltage divider formed of resistors 38, 39. A feedback resistor 44 is connected between the output of the operational amplifier and the inverting input, the value of the feedback resistor determining the amplification factor. The output of the operational amplifier 40 is further connected to a resistor 43 and to a positive supply bus 52.

The output of the operational amplifier 40 is connected over input resistor 48 to the inverting input of operational amplifier47. The non-inverting input of operational amplifier 47 is connected over resistor 49 to the tap of the voltage divider formed of two resistors 45, 46. The tap point is additionally connected over a controllable resistor with an input terminal 54. Operational amplifier 47 has a feedback circuit which includes capacitor 50 acting as integrating capacitor. The output of operational amplifier 47 is connected over resistor 121 to output terminal A, and further to an output terminal C. A supply resistor 51 connects to positive bus 52.

The fuel injection circuit, in its simplest form, essentially includes a switching stage 55 (FIG. 4) which may, for example, be a monostable multivibrator, controlled by pulses from tachometer generator 23, which preferably is a switch operated by a cam rotating in synchronism with the cam shaft, or crankshaft of the engine. Switch 23 is controlled to close, synchronously with crankshaft rotation, with such frequency that each injection valve 16 has applied thereto an injection pulse upon each other full rotation of the crankshaft. Correction input B is provided which controls the pulse duration of the monostable multivibrator (MMV) 55 in dependence on the mass air flow, as measured by air flow meter 14 (FIG. 1), so that when the air quantity is large, more fuel will be injected, and to maintain the air number I. at a constant value. The output of MMV 55 is connected to a pulse extender stage which includes a storage capacitor 60. Storage capacitor 60 has one of its terminals connected to the collector of a transistor v58, the emitter of which is connected over resistor 59 to positive bus 52. Its base is connected to the output of the MMV 55. The base of transistor-58 is further connected to the input terminal A and to chassis or ground bus 152 over resistor 57. Input terminal A of FIG. 4 and output terminal A of FIG. 3 are interconnected.

The second terminal of storage capacitor 60 is connected to the collector of a discharge transistor 61, which has its base connected to a tap point of a voltage divider formed by resistor 62, 63. Resistor 63 is a variable resistor. The emitter of the discharge transistor 61 is connected over a resistor 64 with positive bus 52. The collector of discharge transistor 61 is connected over a diode 65 to the base of an inverter transistor 67. Diode 65 is so poled that the collector current of the discharge transistor 61 is passed thereby. The base of the inverter transistor 67 is connected to chassis over resistor 66. The collector of inverter transistor 67 is connected to the positive bus 52 over collector resistor 68.

The output of MMV 55 and of the collector of inverter transistor 67 is connected, respectively, with two inputs of an OR gate 56 which is connected ahead of a switching transistor 69. Switching transistor 69 controls solenoid 70, which operates the injection valve 16.

Operation: the basic operation of the fuel injection system of FIG. 4 is well known, see the cross reference US. Pat. No. 3,483,851 Reichardt. Only so much of the operation will be described as is necessary for an understanding of the present invention and is not already obvious from prior publications.

The duration of the output pulses from MMV 55 depends on the mass air flow through the induction duct 13. The output pulse of MMV 55 is applied directly to OR gate 56 and then to the switching amplifier 69. The switching amplifier will be energized, in turn energizing solenoid 70 and opening the fuel injection valve to inject fuel. The pulse applied to the OR gate 56 is extended by the extension pulse derived from the extension stage formed of transistors 58, 61, and the inverting transistor 67. The duration of the extension pulse is proportional to the duration of the initial pulse, that is, the duration of the output pulse of MMV 55. Additionally, the duration of the extension pulse is modified by other parameters, for example by the variable resistor 63 which, for example, is a negative temperature coefficient resistor, located in temperature-sensing relationship to the engine and measuring engine temperature. Additionally, the duration of the extension pulse can be modified by other parameters, for example by parameters applied in the form of control voltages connected to terminal A. The voltage applied to terminal A influences the charging current to the capacitor 60, over transistor 58, while the MMV 55 provides its output pulse. Thus, the level of voltage rise, or the level of voltage change which is transferred at the end of the output pulse of the MMV 55 over capacitor 60 is influenced thereby. The resistor 63, however, influences the discharge current of capacitor 60, and thus the time after inverter transistor 67 again becomes conductive, having previously been blocked.

The base electrodes of the two transistors 58, 61 can have other correction potentials applied thereto, for example to obtain enrichment of the fuel-air mixture during warm-up of the engine, upon starting, or the like. The inverter transistor 67 is conductive in quiescent state. Transistor 67 can be blocked if a negative pulse is applied from capacitor 60. The utilization signal on the collector of transistor 67, therefore, just like the output signal of the MMV 55 is a l-signal, that is, it has the value of the voltage at positive bus 52. OR gate 56 thus provides a l-signal at its output when one of its inputs has a l-signal. The output pulse of the pulse extension stage thus follows the output pulse of the MMV 55 so that the output from OR gate 56 will be one continuous pulse, the duration of which is determined by the pulse duration from MMV 55, and the pulse duration of the extension pulse.

Let it be assumed that the duration of the output pulse of the circuit (FIG. 1; FIG. 4) is somewhat too long. Thus, the amount of fuel injected is excessive, and the mixture applied to the engine becomes too rich. Air number A will be less than 1, and the output voltage of sensor 22 will be high.

The output voltage of sensor 22 is amplified in operation amplifier (FIG. 3) which, being connected as an inverter amplifier, provides a negative value of output voltage which is connected over input resistor 48 to the inverting input of operational amplifier 47. This operational amplifier is connected as an integrating amplifier, and thus integrates (at negative input voltage to its inverting input) in positive direction The voltage at terminal A slowly changes in positive direction. As the voltage at terminal A changes towards a positive point, the charging current for the capacitor 60 (FIG. 4) flowing through transistor 58 becomes smaller. This decreases the pulse duration of the extension pulse from the pulse extension stage, so that the overall pulse available at the output of the OR gate 56 becomes shorter, since a shorter extension pulse is added to the base pulse from MMV 55. Solenoid 70 is thus energized for a shorter period of time and less fuel is injected. The mixture becomes leaner until an air number A 1.0 is obtained. At that point, the sensor 22 switches abruptly, to a low output voltage; operational amplifier 47 will now integrate in reverse direction, and the above described cycle will repeat, in reverse direction, so that the duration of the output pulses from the pulse extension stage will increase.

The output voltage of sensor 22 thus corrects deviations of theair number it from the value A 1.0.

Under certain operating conditions, for example upon starting the engine when it is warm, or, for example to protect the catalyst if the ignition partly fails, then it has been found that the control range of the apparatus as described is not sufficient to effectively control the air number A completely.

Referring next to FIG. 6: the normal operating range of the controller described so far is within the limits indicated by the heavy lines 80, 81. The output voltage of the controller is indicated by line 82. As can be seen from FIG. 6, the output voltage of the control amplifier changes in dependence on the output voltage of the sensor 22, that is, it rises or drops. The portion of the curve indicated at 83 shows rapid rise of the output voltage of the controller. The rise in voltage is, however, limited by the operating voltage of the control amplifier. Under such operating conditions it has been found desirable to change the entire operating range, so that the operating range will shift to that indicated between lines 80 and 84. This shift in the control range can be obtained only when the input terminal A of the switching circuit of FIG. 4 has an electrical signal applied thereto in such a manner that the base voltae of the transistor 58 is shifted in a direction to extend the opening times of the fuel injection valves, as commanded by the transistor circuit of FIG. 4.

The control amplifier can operate normally in the control range determined by the limits of lines and 841, as can be seen in curve portion 86. A shift in the control range in the other direction is also possible. Thus, the pulse duration can be shortened, basically, by an electrical signal at input terminal A of FIG. 4 in a direction to change the control range, with equal output voltage of the amplifier itself, by a predetermined value, so that the injection periods will be, inherently, shortened. Thus, for example, the control range can be shifted to fall between lines 81 and 84.

FIG. 5 is a circuit diagram of the circuit to change the correction signal applied to the base of transistor 58 of the circuit of FIG. 4, if operating parameters or conditions of the engine indicate that it is desirable to shift the operating range. The circuit of FIG. 5 includes a first operational amplifier 105, connected as a threshold switch. The output of operational amplifier is connected, over resistor 107, to a positive bus 120. Further, a feedback resistor 106 connects to the noninverting input of the operational amplifier 105 which, further, is connected to a control terminal C of controller 24 (FIG. 3) that is, directly to the output of operational amplifier 47 (FIG. 3). The inverting input of operational amplifier 105 is connected, over an input resistor 103, to the tap point of a voltage divider formed of resistors 101, 102, connected between positive bus 120 and chassis or ground connection 152. The output of operational amplifier 105 is connected over resistor 108 to the base of a first transistor 111, the emitter of which is connected to negative bus 152. A resistor 109 is connected across the base-emitter junction of transistor 111. The collector of transistor 111 is connected over collector resistor to positive bus 120, and further, over a coupling resistor 112 to the base of a transistor 114, the emitter of which is connected to positive bus 120, in parallel to a base-emitter resistor 113. The collector of transistor 114 is connected over coupling resistor 115 and diode 122 to terminal A (FIG. 4), that is, to the base of transistor 58 of the transistor circuit 25 (FIG. 4).

A second threshold switch is connected similarly to the just described threshold switch, and in parallel thereto, the input of which is likewise connected to output terminal C of the control amplifier (FIG. 3). Similar elements have been given similar reference numerals, incremented by 100. The major difference between the circuits is that the final transistor 214 of the parallel circuit is of the reverse conductivity type (npn) to that of transistor 114, and that, therefore, the base-emitter resistor is connected to chassis bus 152, rather than to positive bus 120. The output from the collector resistor 215 connects over diode 123, which is reversely poled with respect to diode 122 to terminal A.

Operation of circuit of FIG. 5, with reference also to FIG. 6: the control voltage derived from control amplifier 24 (FIG. 3) normally has the voltage range falling between lines 80, 81 (FIG. 6), for example having the wave shape indicated by the curve 82. Under certain operating conditions, however, this control range is not sufficient. When the output voltage of control amplifier 24 exceeds a switching threshold indicated by line 88, then a signal is applied over one of the threshold switches 105, 205, to the base of the transistor 58 (FIG.

4) which changes the base voltage thereof, and thus changes the operating range, or control range. When the voltage drops below a certain threshold, for example indicated by broken line 85 (FIG. 6) one of the threshold switches 105, 205 will change back to its initial state, and the base potential of the transistor 58 will again fall within the original value which determines the normal control range. The relationships are similar when the output voltage of control amplifier 24 falls below a threshold, as indicated for example by broken line 87. The other one of the threshold switches 105, 205, respectively, will then change over in order to change the fixed base potential on transistor 58 (FIG. 4) in opposite direction, in order to change the control range downwardly. Thus, the base, or level of extension of the pulse from MMV 58 is changed by changing the charge time taken to charge capacitor 60, and thereby changing the duration of opening time of the fuel injection valve to shorten this injection time. When the voltage reaches the value indicated by chain dotted line 89, one of the two threshold switches 105, 205 will change back to its output state, and the normal base voltage of transistor 58 will again revert to its normal value, and the fuel injection system will operate in its normal range.

As can be seen from FIG. 6, the range of control is substantially extended. Curve 82 shows operation within a normal range, but curve section 83 shows that the mixture is much too lean and requires rapid enrichment. Since this requirement of rapid enrichment exceeds the threshold level 88, the circuit of FIG. will become effective and the control range will be shifted upwardly and the resultant control curve is seen at 86. The rapid enrichment caused an overshoot, however, and rapid dropping is commanded, and the threshold level indicated by broken line 85 will be quickly reached, the circuit switching then to normal level, the control being indicated by curve 82, within its normal range. If too much fuel is still supplied, and the time should be shortened so that the curve 82' drops below the threshold limit given by chain dotten curve 87, the level will shift and the control will then be effected as seen by curve 86', which will persist until the upper threshold level is reached at chain dotted line 89, to reestablish operation within the normal control range, as seen by curve 84" The extent of shift of the control ranges is indicated by broken line 88' and chain dotted line 87, that is, from threshold limit 88 to limit 84; from lower threshold limit 85 to 88 (which is a similar jump); and from lower limit 87 to 84' and from the higher limit in the lower range, 89 to 87.

Various changes and modifications may be made within the scope of the inventive concept.

FIG. 7 illustrates the system as applied to a carburetor fuel system, in which the auxiliary control of air is given by a bypass. Fuel induction tube 713 corresponds to air inlet pipe 13, and applies air to the intake manifold of an internal combustion engine. Fuel is supplied over line 717 to a carburetor 716. A bypass 720 bypasses air around the Venturi of the carburator system, which is indicated only schematically. The bypass 720 includes a bypass throttle or flap valve 721 which, for normal setting of the carburetor, is, for example, half open. It is maintained in this position by a set spring, not shown. Fuel flap valve 721 is mechanically connected, as schematically indicated by chain dotted line 722 to a setting disk 723, which can be deflected from its center position, in either direction, backwards or forwards, by means of a solenoid operated link. The solenoid 724 is energized, in polarized direction, to move the link 725 to the right, or to the left, depending on the polarity of the output signal available from terminal A. Suitable amplification, power, and matching circuits (not shown) may be interposed between terminal A and solenoid 24. Of course, other systems may be used, such as a bi-directional motor, driven directly or indirectly from the output terminal A, or the like. Similarly, rather than controlling the air flow in order to control the proportion of air to fuel, the rotating disk 723 can be connected to a setting or adjustment screw within the carburetor 716 to control the fuel flow through the carburetor to the induction duct 713, independently of other carburetor settings, for example by additionally modifying the setting of the idle jet thereof, when the normal control range of the system is being exceeded.

We claim:

1. Method to reduce the noxious components in the exhaust emission of internal combustion engines having an air-fuel proportion adjustment means, and including an integrating controller carrying out the step of regulating the mass-ratio of air and fuel being applied to the internal combustion engine, utilizing the steps of sensing the composition of exhaust emission and deriving a sensing signal;

integrating the sensing signal and deriving a fuelair ratio control signal;

sensing an operating parameter, or condition of the engine;

and wherein the improvement comprises the steps of changing the control range of the control of air-fuel proportion as a function of change of the sensed operating parameter beyond a predetermined limit.

2. Method according to claim 1 wherein the apparatus includes a fuel-air mass control means;

wherein the step of changing the control range of the air-fuel proportion comprises the step of changing the base setting of said control means.

3. Method according to claim 2 wherein said control means comprises a fuel injection apparatus;

and said step of changing the control range comprises changing the base setting affecting the operating time of the injection system, during which fuel is injected.

4. Method according to claim 2 wherein the control means comprises a carburetor system supplying a predetermined amount of fuel for a predetermined amount of air flow to the induction duct of the internal combustion engine, wherein said step of changing the control range of the air-fuel proportion comprises changing the base setting of at least one of: air flow; fuel flow;

of the carburetor system.

5. Method according to claim 1 wherein the step of sensing an operating parameter of the engine comprises sensing a threshold level corresponding to said limit of the integrated fuel-air ratio control signal;

and the step of changing the control range of the proportion of air and fuel comprises the step of abruptly changing the operating range in a positive, or negative direction if an upper, or lower sensed threshold level is exceeded.

6. Apparatus to reduce the noxious components in the exhaust emission of internal combustion engines comprising means controlling the mass ratio of air and fuel being supplied to the internal combustion engine;

means including an exhaust gas sensor (22)B sensing operating parameters of the engine, including the compositon of exhaust gases therefrom;

and means (24) including an integrator (47,50) connected to and controlled by said exhaust gas sensor and providing an integrated output signal representative of deviation of the signal from the exhaust gas sensor from a predetermined value, said output signal being applied to said mass ratio control means to affect the proportion of air and fuel being applied to the internal combustion engine to reestablish exhaust gas emission from the engine resulting in a predetermined output signal;

the improvement wherein the engine operating parameter or condition sensing means includes limit sensing means (105,205) connected to said means controlling the mass ratio of air-fuel supplied to the internal combustion engine to change the base setting thereof and thus change the control range in which said integrated output signal becomes effective when the integrated signal reaches a predetermined limit as sensed by said limited sensing means.

7. Apparatus according to claim 6 wherein said limit sensing means comprises a threshold switch (105,205), having upper and lower threshold sensing levels and providing an output signal to change the base setting of said mass ratio control means, in either direction, if the upper, or lower threshold is exceeded.

8. Apparatus according to claim 7 wherein the means controlling the mass ratio of air and fuel supplied to the engine comprises a fuel injection system;

and said threshold switch changes a circuit parameter within the fuel injection system in the circuit thereof affecting the duration of injection time of fuel, in a direction to lengthen, or to shorten said injection time to extend the control range of said fuel injection system.

9. Apparatus according to claim 7 wherein said means controlling the mass ratio of air and fuel being supplied to the engine comprises a carburetor system;

electrical-mechanical transducer means are provided, said transducer means having an output controlling the base setting of at least one of: air flow; fuel flow of the carburetor system, said threshold switch energizing said transducer, to increase, or decrease the base setting of a base quantity of air, or fuel, respectively, upon response of the threshold switch, indicative that the normal control range of the carburetor system should be changed.

10. Apparatus according to claim 6 wherein said means sensing an operating parameter of the engine comprises means responsive to changes in the exhaust gas composition, from a predetermined value, over a time. 

1. Method to reduce the noxious components in the exhaust emission of internal combustion engines having an air-fuel proportion adjustment means, and including an integrating controller carrying out the step of regulating the mass-ratio of air and fuel being applied to the internal combustion engine, utilizing the steps of sensing the composition of exhaust emission and derviving a sensing signal; integrating the sensing signal and derving a fuel-air ratio control signal; sensing an operating parameter, or condition of the engine; and wherein the improvement comprises the steps of changing the control range of the control of air-fuel proportion as a function of change of the sensed operating parameter beyond a predetermined limit.
 2. Method according to claim 1 wherein the apparatus includes a fuel-air mass control means; wherEin the step of changing the control range of the air-fuel proportion comprises the step of changing the base setting of said control means.
 3. Method according to claim 2 wherein said control means comprises a fuel injection apparatus; and said step of changing the control range comprises changing the base setting affecting the operating time of the injection system, during which fuel is injected.
 4. Method according to claim 2 wherein the control means comprises a carburetor system supplying a predetermined amount of fuel for a predetermined amount of air flow to the induction duct of the internal combustion engine, wherein said step of changing the control range of the air-fuel proportion comprises changing the base setting of at least one of: air flow; fuel flow; of the carburetor system.
 5. Method according to claim 1 wherein the step of sensing an operating parameter of the engine comprises sensing a threshold level corresponding to said limit of the integrated fuel-air ratio control signal; and the step of changing the control range of the proportion of air and fuel comprises the step of abruptly changing the operating range in a positive, or negative direction if an upper, or lower sensed threshold level is exceeded.
 6. Apparatus to reduce the noxious components in the exhaust emission of internal combustion engines comprising means controlling the mass ratio of air and fuel being supplied to the internal combustion engine; means including an exhaust gas sensor (22)B sensing operating parameters of the engine, including the compositon of exhaust gases therefrom; and means (24) including an integrator (47,50) connected to and controlled by said exhaust gas sensor and providing an integrated output signal representative of deviation of the signal from the exhaust gas sensor from a predetermined value, said output signal being applied to said mass ratio control means to affect the proportion of air and fuel being applied to the internal combustion engine to re-establish exhaust gas emission from the engine resulting in a predetermined output signal; the improvement wherein the engine operating parameter or condition sensing means includes limit sensing means (105,205) connected to said means controlling the mass ratio of air-fuel supplied to the internal combustion engine to change the base setting thereof and thus change the control range in which said integrated output signal becomes effective when the integrated signal reaches a predetermined limit as sensed by said limited sensing means.
 7. Apparatus according to claim 6 wherein said limit sensing means comprises a threshold switch (105,205), having upper and lower threshold sensing levels and providing an output signal to change the base setting of said mass ratio control means, in either direction, if the upper, or lower threshold is exceeded.
 8. Apparatus according to claim 7 wherein the means controlling the mass ratio of air and fuel supplied to the engine comprises a fuel injection system; and said threshold switch changes a circuit parameter within the fuel injection system in the circuit thereof affecting the duration of injection time of fuel, in a direction to lengthen, or to shorten said injection time to extend the control range of said fuel injection system.
 9. Apparatus according to claim 7 wherein said means controlling the mass ratio of air and fuel being supplied to the engine comprises a carburetor system; electrical-mechanical transducer means are provided, said transducer means having an output controlling the base setting of at least one of: air flow; fuel flow of the carburetor system, said threshold switch energizing said transducer, to increase, or decrease the base setting of a base quantity of air, or fuel, respectively, upon response of the threshold switch, indicative that the normal control range of the carburetor system should be changed.
 10. Apparatus according to claim 6 wherein said means sensing an opErating parameter of the engine comprises means responsive to changes in the exhaust gas composition, from a predetermined value, over a time. 